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Okadaic acid disrupts synaptic vesicle trafficking in a ribbon-type synapse
Cristina Guatimosim1, Court Hull, Henrique Von Gersdorff
1Departmento de Farmacologia, ICB, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil. cguati@icb.ufmg.br
Journal of Neurochemistry
|October 3, 2002
Summary
Persistent phosphorylation, induced by okadaic acid (OA), impairs vesicle mobility at ribbon synapses. This suggests phosphatases, particularly phosphatase 2A (PP2A), play a key role in regulating vesicle trafficking in these specialized neuronal connections.
Area of Science:
- Neuroscience
- Cell Biology
- Synaptic Physiology
Background:
- Protein phosphorylation is crucial for synaptic transmission and plasticity.
- Vesicle trafficking regulation at the plasma membrane, especially in ribbon synapses, remains poorly understood.
- The specific role of phosphorylation in ribbon synapse vesicle dynamics is largely unknown.
Purpose of the Study:
- To investigate the impact of persistent phosphorylation on vesicle cycling in goldfish bipolar cells.
- To determine how phosphatase inhibition affects vesicle translocation at ribbon synapses.
Main Methods:
- Utilized the phosphatase inhibitor okadaic acid (OA) in goldfish bipolar cells.
- Monitored vesicle recycling using FM1-43 uptake assays.
- Measured exocytosis and endocytosis kinetics via capacitance measurements.
Main Results:
- Okadaic acid (OA) dose-dependently inhibited the spatial spread of FM1-43 within synaptic terminals.
- Capacitance measurements showed OA did not alter the quantity or speed of exocytosis and endocytosis.
- Low OA concentrations implicated phosphatase 2A (PP2A) in regulating post-endocytic vesicle trafficking.
Conclusions:
- Phosphatases, specifically PP2A, are critical regulators of vesicle translocation at ribbon synapses.
- Unlike conventional synapses, phosphatases inhibit rather than enhance vesicle mobility at ribbon synapses.
- This study reveals a distinct mechanism of vesicle trafficking regulation at ribbon synapses compared to the neuromuscular junction.